1. Field
The following description relates to a battery thermal management method and system.
2. Description of Related Art
Lithium ion (Li-ion) batteries provide an option of low weight, high energy density, and slow discharge rates, as compared to other battery technologies. These advantages of the Li-ion batteries, has made them desirable for high energy demanding applications such as electric vehicles. The energy held by lithium-ion cells is multiple times than that of conventional lead acid or nickel cadmium batteries. However, a lithium-ion battery has an inherent problem of overheating leading to thermal runaway. Li-ion battery degrades faster at high temperatures and offers low capacity at low temperature. At very high temperature, the thermal runaway may be triggered in the Li-ion battery due to unwanted exothermic reactions in organic electrolytes. The Li-ion battery typically works best in a narrow band of temperature close to human comfort zone and typically elaborate thermal management systems are used in order to maintain the operating temperature in that band. Thus thermal management may enable maintenance of battery performance, improved battery life, and addresses safety concerns.
Such typical thermal management approaches implement feedback controlled thermal management, i.e. only after a measured temperature of a battery or battery pack exceeds a set threshold, a cooling system is actuated to cool the batteries or the battery pack to below the threshold. However, due to the inherent dependence of the battery electrochemical processes on temperature and the resulting delay before the battery cooling operation is implemented, this typical approach results in higher heat dissipation and inefficient operation. Further, such existing approaches for thermal management do not consider alternate features for thermal management, hence they mostly fail to provide accurate control over operating temperature of the battery.
For example, as noted, in general the thermal management of large battery pack is primarily done through feedback control. However, the heat generation in the battery pack is strongly related to State of Charge (SoC) of the batteries and the discharge rate. Thus, existing feedback control based thermal management approaches fail to provide efficient cooling as they do not predict heat generation by the batteries. This may results in overheating or overcooling of the battery and may lead to hazardous situations.